Counterboring tool



A 1929- A. L. CHRlSTENSEN 1,724,005

COUNTERBORING TOOL Filed June 20 1925 IN V EN TOR.

' ATTORNEY Patented Aug. 13, 1929.

PATENT OFFICE.

ANKER L. CHRISTENSEN, OF NEW YORK, N. Y.

GOUNTERBORING TOOL.

Application filed June 20, 1925.

This invention relates to cutting tools and more particularly to counterboring tools of the interchangeable type.

An object of the invention is to provide a simple and effective tool for counterboring.

One of the important features of the 111- vention relates to the provision of inter changeable parts which may be assembled in a variety of combinations so as to produce desired counterbores in accordance with the requirements of the work, and adapted to be easily modified in a simple and expeditious manner whenever the character of the work requires it.

Another feature of the invention relates to the provision of means for positively centering the tool so as to produce work of in creased accuracy and precision.

Still another object relates to the provision of driving means operatively interconnecting the parts of the tool positioned at a maximum distance from the principal axis of the tool.

Still another feature relates to the provision of a driving holder of predetermined diameter with respect to the diameter of the cutter, so that the tool may be readily operated to increased depth in the metal being worked upon.

Another feature relates to the provision of means for maintaining the tool parts in assembled position with increased ruggedness and stability. According to this feature the tool parts are retained in predetel-mined relative position by a retaining bolt normally held under tension.

Another important feature of the invention is the provision of a counterboring tool of simple construction which is economical to manufacture and which may be readily formed of conventional raw material readily available in the market.

Other objects will appear from the following description taken in connection with the accompanying drawings, in which Figure l is an elevation partly in section of one "form of the invention;

Figure 2 is a perspective View of the parts shown in Figure 1 in'dismantled position;

Figure 3 is a transverse sectional View of the cutting tool of Figure '1, taken 011 the line 3-3 of Figure 1;

Figure 4 is an elevation partly in section The end 12 of Serial No. 38,420.

of a modified form of the pilot shown in Figure 1;

Figure 5 is an elevation of an indeterminate length of raw material from which the cutting tool of Figure 3 is constructed;

Figure 6 is a section taken on the line 6-6 of Figure 5; and

Figure 7 is an elevation of two of the cutting tools of Figure 3 during an intermediate step of the processes of making the same.

Figures 8 and 9 are side and end elevations respectively of the cutter.

Like reference characters refer to like parts in the several figures of the drawings.

In the following description and claims, parts will be identified by specific names for convenience of expression, but they are intended to be as generic in their application to. similar parts or equivalent construction as the art will permit.

Referring to Figure 1, there is provided a counterboring tool of the interchangeable type comprising a driving holder or mandrel 10 formed of a tapered shaft of suitable material such as hard steel. One of the ends of the holder 10 is formed as at 11 to cooperate with a suitable driving element or other source of power (not shown). relatively large diameter is provided withatapped drill hole 13 extend ing a predetermined distance into the shaft upon the longitudinal axis thereof. The end 12 of the holder is also provided with an, internal bore or recess 14 relatively greater in diameter than the drill hole 13 but sufliciently less in diameter than the end 12 of the shaft 10 to form a skirt 15, the outer end of which is notched as at 16, 17 18 and 19 (see Figure 2) for a purpose which will subsequently be set forth.

' The method of forming the cutting element or cutter will now be described. An indeterminate length of raw material such as shown in Figures 5 and 6 is taken and is cut into sections each substantially twice the length of two of thefinished cutters. The raw material may consist of a bar of tool steel having longitudinal splines 22 extending parallel to the axis of the bar. Each end of each sect-ion is then turned down to form cylindricali portions 20. The diameter of the cylindrical portions 20 is preferably equal to or slightly larger than the distance between the diametrically opposite depressions which are located between the splines 22. Each cylindrical portion is of such diameter as to fit snugly within the base 14.

The sectionwhich is denoted by 21, is then heated to a forging temperature toallow the section to be twisted to cause the splines 22 of the bar to define helices. The angle which the heliX makes with the longitudinal axis of the section may be any angle which, in practice, proves efiicient. For example the angle of 10 degrees may be used. In the event high speed steel, containing from 1% to 18% tungsten is used, a forging temperature of approximately 1800 degrees Fahrenheit may be employed:

- The section 21 is then out along the dividing line 23 to form two cutters, each denoted generally by 2-l. Each cutter is then hardened in any er the well known ways.

The end faces of the splines at the cutting end of the cutter 24 are then cut or ground to form cutting edges 25 and to provide an appropriate clearance or rake 26. Similarly, the side faces of the splines 22 are 'cut or ground away as at 27 to allow clearance space." I

The cutting'or grinding away of the side and end faces of the splines may be done either before or after the hardening. However, the sharpening of the tool or cutter by cutting away the end faces of the splines to form new cutting edges 25 is preferably done after; hardening.

In order to guide the tool into the hole which is to be counterbored, a pilot is provided'. In Figure 1, one form of pilot is shown and is denoted by 28. It has a cylindrical outer surface 29 and has one edge rounded as'at 30. It has a cylindrical here into which snugly fits the shank 31 of a retaining bolt 32. i

The leader 10, cutter'2-ii and pilot 28 are all clamped securely together by means of bolt 32. The end of the bolt 32 is provided with screw threads 33 which engage the screw threads in the hole 13. The bolt is provided with a wrench-engaging head 3% 'by' means of which the bolt is threaded ti htly into" the holder 10, thereby placing the bolt under tension.

The cylindrical portion -20 of the cutter preferably registers with the bore 1d and the ends of the splines 22 fit into the notcheslG, 17 18 and l9g'which positively prevent'relative rotation of the holder 10 and the cutter 24. The notches--16, 17, 18 and 19 are preferably cut'int'o the skirt'15; to define a portionof= a helix of the same pitch as that to-which the splines 22 define.

Referring now to Figure 4, the pilot 28 is shown as capable of rotation onthe bolt 32' so as to obviate all possibility of the pilot seizing the metalsurrounding the hole at is desired to counterslnleor counterbore.

ent specific description.

In this modification, the cutter 24; is the same as before but the bolt is modified to accommodate the modified form of pilot. The bolt 32 is provided with an enlarged cylindrical portion adjacent the head 341 to provide a journal on which pilot 28 can rotate. The journal is slightly longer than the pilot 28 to insure that the pilot will be free to rotate even after the bolt 32' is threiuled tightly into the hole 13 and the slmulder 36 formed by the end of the journal presses the cutter 24s tightly against the holder 10.

It will be appreciated that the purpose of the pilot is to guide the tool into the hole it is desired to counter-bore or countersink so that the countersunk portion will be concentric with the hole. Hence the diameter of the pilot must be such that the fit is sung and yet the pilot will not seize the metal surrounding the hole.

It will be seen that with my arrangement, any size cutter may be used with any size pilot. Also the cutter is always larger than the diameter of the holder 10, so that, if the counter-bore deep, there will be adequate clearance between the sides of the hole and the holder.

Thus it will be seen that I have provided a cutting tool havil'ig cutting edges which are disposed in staggered relation with each other and with respect to the center of the cutter. l have thus provided a cutting tool with an even number of cutting teeth and which, in practice does not produce undesirable chatter.

The arrangement of the cutting edge with respect to the center of the cutter is such that each cutting edge is spaced apart from the radial line and thus a shearing action is effected for cutting away the metal being operated upon.

The inv .ition upon which this application is based is broader than the specific embodiment shown and described for the purpose of illustrating at least one of the ways in which it may be employed. The scope of the invention is therefore to be understood as not being limited by the pres- I intend no limitations other than those imposed by the claims.

What I claim is:

1. A counterboring tool comprising a holder, a cutter having a plurality of cut ting edges, a pilot consisting of a cylindrical member adapted to lit into the hole to be counterbored, a securing bolt extending through said cutter and said pilot into engagement with the holder and having a wrench engaging head forming a first abutment, a reduced cylindrical journal extending from said abutment to a second abutment formed by the further reduced shank, said pilot loosely engaging said journal, and means whereby said bolt operates to hold said second abutment against said cutter and said cutter against said holder.

2. A tool comprising a holder having a screw threaded socket and a concentric centering bore, the material surrounding said bore forming a skirt having a plurality of notches in its end face, a cutter having a plurality of generally longitudinally extending, but slightly helical, splines fitting into said notches and having a cylindrical centering projection fitting into said bore, said cutter having a longitudinal hole therethrough, the splines of said cutter having their end faces cut to form cutting edges, and means for securing said cutter to said holder including a retaining bolt having a screwthreaded shank extending through the hole in said cutter and fitting into said SOl'GWtlll'GtlClfiCl socket.

3. A tool comprising a holder having a centering bore, the material surrounding said bore forming a skirt having a plurality of notches in its end face, a cutter having a plurality of generally longitudinally extending splines fitting into said notches and having a cylindrical centering projection fitting into said bore, the splines of said cutter having their faces cut to form cutting edges, and means whereby said cutter is secured to said holder.

4:. A metal working tool comprising a shank having a bore to form a recessed end, and having a plurality oi notches cut in the periphery of the shank around the bore, said notches having their sides lying on a helix of predetermined pitch, a cutter having a corresponding plurality of peripheral splines each defining av helix of the same pitch, said splines engaging said notches respectively to form a rigid driving engagement between the shank and the cutter.

5. A metal working tool comprising a shank having a bore to form a recessed end, and having a plurality of notches cut in the periphery of the shank around the bore to define a helix of predetermined pitch, a cutter having a corresponding plurality of peripheral splines each defining a helix of the same pitch, and each engaging at one portion a corresponding notch, and having a different portion ground to form a cutting edge.

6. A metal working tool comprising a; shank having a bore to form a recessed end, and having a plurality of notches cut in the periphery of the shank around the bore to define a. helix of predetermined pitch, a cutter having a corresponding plurality of peripheral splines each defining a helix oi the same pitch, said splines engaging said notches respectively to form a rigid driving engagement between the shank and the cutter, and means under tension for maintaining the cutter in fixed relation to the shank.

7. A metal working tool comprising a shank having a bore to form a recessed. end, and having a plurality of notches cut in the periphery of the shank around the bore to define a helix of predetermined pitch, a cutter having a corresponding plurality of peripheral splines each defining a helix of the same pitch, said splines engaging said notches respectively to form a rigid driving engagement between the shank and the cut ter, and a bolt extending through the cutter into the bore of the shank for limiting longitudinal movement of the cutter with respect to the shank.

8. A tool holder comprising a shank hav ing a cupped end, the rim of the cup having notches provided therein, a cutter having longitudinal ribs, each rib engaging one of said notches to form a rigid driving engagement between the shank and the cutter, said ribs having cutting edges provided thereon.

Signed at New York City, in the county of New York and State of New York, this 18th day of June, A. D. 1925.

ANKER L. CHRISTENSEN. 

